This evening people around the world will witness a rare celestial event - a solar eclipse, which occurs when the moon passes between Earth and the sun.

Those who are standing directly in the moon's shadow on Earth on August 21, will see the disc of the moon move slowly in front of the sun until it covers it completely, leaving only a burning ring of light around the edge.

Those who are not in the right place to witness a total eclipse may still see a partial eclipse. The sky will darken and the temperature will drop, as the moon obscures part of the sun from view.

(Image: Rex Features)

Solar eclipses don't come along every day, so if you're keen to see the spectacle, it's worth planning ahead to make sure you're in a good position for when it happens.

Here's what you need to know about the 2017 total solar eclipse.

What is a solar eclipse?

(Image: Getty)

A solar eclipse occurs when the moon passes between Earth and the sun, obscuring the sun from view.

When the disk of the moon appears to completely cover the disk of the sun in the sky, it is known as a total solar eclipse. If part of the sun is still visible, it is known as a partial solar eclipse.

Solar eclipses occur because the moon orbits the Earth at an average of 239,000 miles - which is just the right distance for it to appear the same size in the sky as the much larger sun, which is 93 million miles away.

The amazing coincidence means that, when the moon passes in front of the sun, it is appears to cover it perfectly.

Where can I watch the solar eclipse?

The best place to see the solar eclipse is in the United States. The so-called "path of totality", which describes the areas where a total solar eclipse is visible, passes right through the middle of the country.

If you want to see a total eclipse, you'll need to be in one of 11 US states - including Idaho, Wyoming, Nebraska, Kansas, Missouri, Illinois, Kentucky, Tennessee, Georgia, North Carolina and South Carolina.

(Image: Reuters)

The rest of the United States will witness a partial solar eclipse. The amount that the moon covers the sun will vary depending on where the viewer is standing.

As for those of us in Ireland, we will also witness a partial solar eclipse - although it may be a little underwhelming , as only 4% of the sun will be covered by the moon.

The total solar eclipse will of course be available to view live on the NASA website .